<html xmlns="http://www.w3.org/1999/xhtml" xmlns:html="http://www.w3.org/1999/xhtml">
<head>
<bindings xmlns="http://www.mozilla.org/xbl">
  <binding id="foo" extends="html:input">
    <content>
      Foo?
      <children/>
    </content>
  </binding>
</bindings>
</head>

<body>
<div>Hi!</div>
<div style="-moz-binding: url(#foo)">XXX</div>
</body>

</html>